/Engine/Plugins/Experimental/UIFramework/Source/Public/Types/UIFWidgetTree.h
Change the parent / child relationship of the child widget. If the child widget had a parent, that relationship entry will replaced it by a new one.
void AuthorityAddWidget ( [UUIFrameworkWidget](API\Plugins\UIFramework\UUIFrameworkWidget) * Parent, [UUIFrameworkWidget](API\Plugins\UIFramework\UUIFrameworkWidget) * Child )